It was told about the most common types of fiber optic cable used in Ukraine. And today - a cable in a section, and in the course of the story - some practical moments of its installation.
We will not dwell on the detailed structure of all types of cable. Let's take some average typical OK:
- Central (axial) element.
- Optical fiber.
- Plastic modules for optical fibers.
- Film with hydrophobic gel.
- Polyethylene shell.
- Armor.
- Outer polyethylene sheath.
What does each layer represent when viewed in detail?
Central (axial) element
Fiberglass rod with or without polymer sheath. Main purpose - stiffens the cable. Unsheathed fiberglass rods are bad because they break easily when bent and damage the optical fiber located around them.
optical fiber
Optical fiber strands most often have a thickness of 125 microns (about the size of a hair). They consist of a core (through which, in fact, the signal is transmitted) and a glass shell of a slightly different composition, which ensures complete refraction in the core.
In cable marking, the diameter of the core and sheath is indicated by numbers through a slash. For example: 9/125 - core 9 microns, shell - 125 microns.
The number of fibers in the cable varies from 2 to 144, this is also fixed by a number in the marking.
Based on the thickness of the core, fiber optics are classified into single mode(thin core) and multimode(larger diameter). Recently, multimode has been used less and less, so we will not dwell on it. We only note that it is intended for use over short distances. The sheath of multimode cable and patch cords is usually made orange color(single mode - yellow).
In turn, single-mode optical fiber is:
- Standard (marking SF, SM or SMF);
- Dispersion-shifted ( DS, DSF);
- With non-zero shifted variance ( NZ, NZDSF or NZDS).
In general terms, a dispersion-shifted (including non-zero) fiber optic cable is used over much longer distances than a conventional one.
On top of the shell, the glass threads are varnished, and this microscopic layer also plays an important role. Optical fiber without varnish is damaged, crumbles and breaks at the slightest impact. While in lacquer insulation, it can be twisted and subjected to some stress. In practice, fiber optic strands can withstand the weight of the cable on supports for weeks if all other power rods break during operation.
However, you should not place too high hopes on the strength of the fibers - even varnished, they break easily. Therefore, when installing optical networks, especially when repairing existing highways, extreme accuracy is required.
Plastic modules for optical fibers
These are plastic shells, inside of which there is a bundle of fiber optic filaments and a hydrophobic lubricant. There can be either one such tube with fiber optics in the cable, or several (the latter is more common, especially if there are a lot of fibers). Modules perform the function of protecting fibers from mechanical damage and along the way - their association and marking (if there are several modules in the cable). However, it must be remembered that the plastic module breaks quite easily when bent, and breaks the fibers in it.
There is no single standard for the color marking of modules and fibers, but each manufacturer attaches a passport to the cable drum, in which this is indicated.
Film and polyethylene sheath
These are elements of additional protection of fibers and modules from friction, as well as moisture- some types of optical cable contain a hydrophobe under the film. The top film can be additionally reinforced with interweaving threads and impregnated with a hydrophobic gel.
The plastic shell performs the same functions as the film, plus it serves as a layer between the armor and modules. There are cable modifications where it is not available at all.
Armor
This can be either Kevlar armor (woven threads), or a ring of steel wires, or a sheet of corrugated steel:
- Kevlar used in those types of fiber optic cable where the metal content is unacceptable or if you need to reduce its weight.
- Steel wire armored cable designed for underground laying directly into the ground - strong armor protects against many damages, incl. from a shovel.
- Cable with corrugated armor laid in pipes or cable ducts, such armor can only protect against rodents.
Outer polyethylene sheath
The first and practically the most important level of protection. Dense polyethylene is designed to withstand all the loads that fall on the cable, so if it is damaged, the risk of damage to the cable increases significantly. You need to make sure that the shell:
a) Has not been damaged during installation - otherwise moisture getting inside will increase the losses on the line;
b) Do not touch a tree, wall, corner or edge of a structure, etc. during operation, if there is a risk of friction in this place under wind and other loads.
As you read this, terabytes of data are floating around the world, trapped in strands of glass stretched across the ocean floor. It looks like magic, but it's just advanced technology. Optical fiber is a technology that humanity owes to the naturalists of the 19th century. Observing the rays of light on the surface of the pond, they assumed that the light could be controlled, but it was only recently that they managed to put into practice that brilliant idea with the advent of the most complex factories and a thorough study of the optical properties of materials.
locked light
Twisted-pair copper wire (like your internet cable) has lots of electrons moving around. The current is transmitted through the conductor and carries with it information encoded in a sequence of pulses. Zeros and ones - a binary code that, perhaps, everyone has heard of. The optical conductor of the signal works on the same principle, but from the point of view of physics, everything is much more complicated with it. There could be a half-hour lecture on quantum mechanics, and how many eminent physicists have come to a standstill, trying to understand the nature of light, but we will try to do without lengthy reasoning.
It is enough to keep in mind that, like electrons, photons or light waves (in fact, in our context they are one and the same), can carry encoded information. So, for example, at airfields, in cases of radio communication failure, signals are transmitted to aircraft using directional searchlights. But that is a primitive method, and it only works at a distance of direct visibility. At the same time, light is transmitted by optical fiber for kilometers and far from a straight path.
Mirrors could be used to achieve this effect. Actually, from this test engineers began their experiments. They covered the metal pipes from the inside with a mirror layer and directed a beam of light inside. But not only that, such light guides were prohibitively expensive. The light was repeatedly reflected from their walls and gradually faded, lost its strength and completely disappeared.
The mirrors didn't work. It couldn't be otherwise. Even the most expensive mirror is not perfect. Its reflection coefficient is less than 100%, and after each fall on the mirror surface, the light beam loses some of its energy, and in the closed volume of the fiber, there are an innumerable number of such refractions.
It was then that the time came to recall the pond and those old studies that were based on observing the behavior of light in water. Imagine how a ray of the setting sun falls on the surface of the water, overcomes the boundary and goes down to the bottom of the pond.
Those of the readers who remember the school physics course, probably already guess that the light will change the direction of its movement. Part of the light will pass under the water, slightly changing the angle of its movement, and another insignificant part of the light will be reflected back into the sky, because "the angle of incidence is equal to the angle of reflection." If you observe this phenomenon for a long time, one day you will notice that the light reflected from a mirror under water, at a certain angle, will not be able to break out - it will be completely reflected from the border of water and air, better than from any mirror. The point is not in water as such, but in the combination of two media with different optical properties - unequal refractive indices. To create a light trap, their minimum difference is sufficient.
Flexible light guides
The materials are not that important. Physical experiments for children that demonstrate this effect often use water and a clear plastic tube. More than a couple of meters in such a light guide, the light beam cannot be transmitted, but it looks beautiful. For the same reason, lamps and other decorative items often have plastic light guides in their construction. But when it comes to transmitting information over many kilometers, special, ultra-pure materials are required, with a minimum of impurities and optical properties close to ideal.
In 1934, an American, Norman R. French, patented a glass light guide that was supposed to provide telephone communications, but it did not really work. It took a lot of time to find a material that would meet the highest requirements for purity and transparency, to invent an optical fiber from silicon dioxide - the purest quartz glass. In order to create a difference in refractive indices in transparent silicon, one resorts to a trick. The center of the transparent blank, which will turn into a wire, is left clean, while the outer layers are saturated with germanium - it changes the optical characteristics of the glass.
In this case, the blank is usually sintered from two prefabricated glass tubes inserted one into the other. But you can do the opposite, by saturating the fiberglass core with germanium. A more technologically advanced and high-quality glass fiber is obtained when glass tubes are filled with gas from the inside and wait until germanium itself settles on the glass in a thin layer. Then the tube is heated and stretched to a meter length. In this case, the cavity inside closes itself.
The resulting rod has a core with one refractive index and a shell with different optical parameters. It will then serve for the manufacture of optical fiber. So far, a heavy workpiece as thick as a hand does not resemble a wire, but quartz glass is well stretched.
The prepared blank is raised to a height of a ten-meter tower, fixed on top and evenly heated until it resembles nougat in consistency. Then, under its own weight, the thinnest thread begins to stretch from the glass blank. On the way down, it cools down and gains flexibility. It may seem strange, but ultra-thin glass bends beautifully.
The finished optical fiber, continuously coming down, is dipped into a bath of liquid plastic, which forms a protective layer on the quartz surface, and then wound up. This continues until the blank at the top of the tower is completely processed into a single thread of a hundred or two kilometers of optical fiber.
From this, in turn, cables will be woven, containing from a couple to a couple of hundred individual glass fibers, reinforcing inserts, shielding layers and protective sheaths.
- Axial rod.
- Optical fiber.
- Plastic protection of optical fibers.
- Film with hydrophobic gel.
- Polyethylene shell.
- Reinforcement.
- Outer polyethylene sheath.
Connection with the speed of light
The described process is complex, labor-intensive, requires the construction of factories and special training from their personnel, and, nevertheless, the game is worth the candle. After all, the speed of light is an insurmountable limit, the maximum speed with which information can propagate in principle. Only lines of direct optical communication can compete with optical fiber in the speed of information transfer, but not copper conductors, no matter what tricks their creators use. Comparisons demonstrate the superiority of optical fiber over other means of information transmission in the best way.
Home Internet in the post-Soviet space is often carried out over a twisted-pair cable with conductors one or two millimeters thick. The maximum for it is 100 megabits per second. This is enough for a couple of computers, but when there is a smart TV in the apartment, a NAS that distributes torrents, a home server, several smartphones and smart devices from the world of the Internet of things, an eight-wire wire is not enough. The limitations of the communication channel become apparent. As a rule, in the form of artifacts and stuttering movie characters on the TV screen, or lags in online games. Optical fiber with a thickness of 9 microns has 30 times more bandwidth, not to mention the fact that there can be several such strands in a wire.
At the same time, it is more compact and weighs much less than conventional wires, which is a decisive advantage when laying trunk communication lines and planning urban communications.
Optical cables connect continents, cities and data centers. In Russia, the first such line appeared in Moscow. The first underwater optical cable ran between St. Petersburg and the Danish Aberslund. Then the fiber was stretched between enterprises, government agencies and banks. In large cities, a scheme has become widespread in which optical communication lines are brought to individual apartment buildings, and, nevertheless, for the average consumer, optical fiber is still exotic. We would be interested to know how many of our readers use it at home, because, in most apartments, the good old-fashioned twisted-pair cable still stretches.
Optical fiber is not only expensive and difficult to manufacture. Even more expensive is its qualified service. Here you can not do without blue electrical tape. During installation, quartz fibers must be spliced in a special way, and fiber optic communication lines must be completed with additional equipment.
Despite the fact that the difference in the refractive indices in the core and cladding of the fiber in theory creates an ideal light guide, the light launched through the quartz wire is still attenuated due to impurities contained in the glass. Alas, getting rid of them completely is almost impossible. A dozen water molecules per kilometer of optical fiber is already enough to introduce errors into the signal and reduce the distance over which it can be transmitted.
Electrical engineers face a similar problem with conventional wires. The distance to which you can easily send a signal over the wire they call the regeneration distance.
For a standard telephone cable, it is equal to a kilometer, for a shielded cable - five. The fiber optic core keeps the light at a distance of up to several hundred kilometers, but, in the end, the signal still has to be amplified, regenerated. Relatively cheap and simple amplifiers are installed on classical communication lines. For fiber optics, complex and highly technical units are required that use rare earth metals and infrared lasers.
A small section of specially prepared fiberglass is cut into the communication line. It is additionally saturated with erbium atoms, a rare earth element used, among other things, in the nuclear industry. The erbium atoms in this section of the fiber are in an excited state due to additional pumping by light. Simply put, they are illuminated with a specially tuned laser. The signal passing through such an area of the cable is approximately doubled, since erbium atoms, in response to exposure, emit light of the same wave as the incoming signal, and therefore retain the information encoded in it. After the amplifier, the optical signal can travel about a hundred kilometers before the procedure needs to be repeated.
Such systems require trained personnel for maintenance and constant supervision, so that the economic benefit of laying individual optical lines for specific subscribers remains doubtful in most countries of the world. And yet, we all use fiberglass to convey messages. The entire modern Internet is based on this technology, and it is thanks to it that Internet broadcasts in ultra-high resolution, video streaming, online games with minimal delay, instant communication with almost anywhere in the world, and even mobile Internet have become possible. Yes, fiberglass also links cell phone base stations.
Despite the fact that scientists are looking for new ways to build communication networks, we will not get anything more practical for a very long time. Experimental technologies make it possible to increase the information capacity of fiberglass by two to three times, more and more thick stranded glass cables lie on the seabed between continents, however, it is unlikely that it will be possible to overcome the fundamental limitations imposed by the speed of light locked in a quartz vein. The way out seems to be the rejection of quartz and the limitations associated with it, the transmission of information using lasers, but it is possible only in a straight line. Consequently, the transmitters will have to be placed in space, or at least in the upper atmosphere. Similar experiments have attracted the attention of major corporations in recent years, but that's another story.
In the modern world, it is necessary to transfer information efficiently and quickly. Today, there is no more perfect and efficient way to transmit data than fiber optic cable. If someone thinks that this is a unique development, then he is deeply mistaken. The first optical fibers appeared at the end of the last century, and work is still underway to develop this technology.
To date, we already have a transmitting material that is unique in its properties. Its use has gained wide popularity. Information in our time is of great importance. With the help of it, we communicate, develop the economy and life. At the same time, the speed of information transfer must be high in order to ensure the necessary pace of modern life. Therefore, now many Internet providers are introducing fiber optic cable.
This type of conductor is intended only for the transmission of a pulse of light that carries part of the information. Therefore, it is used to transmit informative data, and not to connect power. Fiber optic cable makes it possible to increase the speed several times, in comparison with metal wires. During operation, it has no side effects, deterioration in quality at a distance, overheating of the wire. The advantage of a cable based on optical fibers is the impossibility of influencing the transmitted signal, so it does not need a screen, stray currents do not affect it.
Classification
Fiber optic cable differs greatly from twisted pair cable in terms of application and installation location. There are main types of cables based on optical fiber:
- For indoor installation.
- Installations in cable channels, without armor.
- Installations in cable channels, armored.
- Ground laying.
- Suspended, without a cable.
- Suspended, with rope.
- For underwater installation.
Device
The simplest device has a fiber optic cable for indoor installation, as well as a cable of a conventional design that does not have armor. The most complex design is for cables for underwater installation and for installation in the ground.
Indoor cable
Internal cables are divided into subscriber cables, for laying to the consumer, and distribution cables for creating a network. Optics are carried out in cable channels, trays. Some varieties are laid along the facade of the building to the switch box, or to the subscriber himself.
The fiber optic device for indoor laying consists of an optical fiber, a special protective coating, power elements, such as a cable. Fire safety requirements are imposed on the cable laid inside buildings: resistance to burning, low smoke emission. The cable sheath material is polyurethane, not polyethylene. The cable should be light, thin and flexible. Many versions of fiber optic cable are lightweight and protected from moisture.
Indoors, the cable is usually laid over short distances, so there is no talk of signal attenuation and the impact on information transmission. In such cables, the number of optical fibers is not more than twelve. There are also hybrid fiber optic cables that contain twisted pair.
Cable without armor for cable ducts
Optics without armor is used for installation in cable ducts, provided that there is no mechanical impact from the outside. This version of the cable is used for tunnels and collectors of houses. It is laid in polyethylene pipes, manually or with a special winch. A feature of this version of the cable is the presence of a hydrophobic filler, which guarantees normal operation in the cable channel, protects against moisture.
Armored cable for cable ducts
An armored fiber optic cable is used when there are loads from the outside, for example, tensile. Armor is done differently. Armor in the form of a tape is used if there is no exposure to aggressive substances, in tunnels, etc. The armor structure consists of a steel pipe (corrugated or smooth), with a wall thickness of 0.25 mm. Corrugation is performed when it is one layer of cable protection. It protects the optical fiber from rodents, increases the flexibility of the cable. Under conditions with a high risk of damage, wire armor is used, for example, at the bottom of a river, or in the ground.
Cable for laying in the ground
To install the cable into the ground, an optical fiber with wire armor is used. Reinforced tape-armoured cables can also be used, but they are not widely used. To lay the fiber in the ground, a cable layer is used. If installation in the ground is carried out in cold weather at a temperature of less than -10 degrees, then the cable is heated in advance.
For wet ground, a cable with a sealed optical fiber in a metal tube is used, and the wire armor is impregnated with a water-repellent composition. Experts make calculations for laying the cable. They determine the permissible stretching, compression loads, etc. Otherwise, after a certain time, the optical fibers will be damaged and the cable will become unusable.
Armor has an effect on the value of the allowable tensile load. Optical fiber with wire armor withstands a load of up to 80 kN, with tape armor, the load can be no more than 2.7 kN.
Overhead fiber optic cable without armor
Such cables are installed on the supports of communication and power lines. So installation is easier and more convenient than in the ground. At the same time, there is an important limitation - during installation, the temperature should not fall below -15 degrees. The cross section of the cable is round. This reduces wind loads on the cable. The distance between supports should be no more than 100 meters. The design has a strength element in the form of fiberglass.
Thanks to the strength element, the cable can withstand heavy loads directed along it. Strength elements in the form of aramid threads are used at distances between poles up to 1000 meters. The advantage of aramid threads, in addition to low weight and strength, is the dielectric properties of aramid. If lightning strikes the cable, there will be no damage.
The cores of overhead cables are different. According to their type, cables are divided into:
- Profile core cable, fiber optic is crush and stretch resistant.
- Cable with twisted type modules, optical fibers are laid freely, there is resistance to stretching.
- With an optical module, the core has nothing other than optical fiber. The disadvantage of this design is that it is inconvenient to identify the fibers. Advantage - small diameter, low cost.
Optical fiber cable with tether
Cable fiber is self-supporting. Such cables are used for laying through the air. The cable is either load-bearing or winding. There are cable models in which the optical fiber is inside the lightning protection cable. The cable, reinforced with a profile core, has sufficient efficiency. The cable consists of a steel wire in a sheath. This sheath is connected to the cable sheath. The free volume is filled with a hydrophobic substance. Such cables are laid with a distance between the poles of not more than 70 meters. The limitation of the cable is the impossibility of laying on the power line.
Cables with a lightning protection cable are installed on high-voltage lines with fixation to ground. Rope cable is used at the risk of damage by animals, or over long distances.
Underwater fiber optic cable
This type of optical fiber is isolated from the rest, because its laying takes place in special conditions. All submarine cables have armor, the design of which depends on the depth of laying and the topography of the bottom of the reservoir.
Some types of underwater optical fiber for the execution of armor with:
- Single armor.
- Reinforced armor.
- Reinforced double armor.
- Without armor.
1› Polyethylene insulation.
2› Mylar coated.
3› Double wire armor.
4› Aluminum waterproofing.
5› Polycarbonate.
6› Central tube.
7› The filler is hydrophobic.
8› Optical fiber.
The size of the armor does not depend on the depth of the lining. Reinforcement protects the cable only from the inhabitants of the reservoir, anchors, ships.
Fiber splicing
For welding, a special type of welding machine is used. It contains a microscope, clamps for fixing fibers, arc welding, a heat shrink chamber for heating sleeves, a microprocessor for control and monitoring.
Brief technical process of fiber optic splicing:
- Removing the shell with a stripper.
- Preparation for welding. Sleeves are put on the ends. The ends of the fibers are degreased with alcohol. The end of the fiber is cleaved with a special device at a certain angle. The fibers are placed in the apparatus.
- Welding. The fibers are aligned. With automatic control, the position of the fibers is set automatically. After confirmation by the welder, the fibers are welded by the machine. With manual control, all operations are carried out manually by a specialist. When welding, the fibers are melted by an electric arc, combined. Then the place to be welded is heated to avoid internal stresses.
- Quality checking. The automatic welding machine analyzes the image of the welding place under a microscope, determines the assessment of the work. An accurate result is obtained by a reflectometer, which detects inhomogeneity and attenuation in the welding line.
- Processing and protection of the welded area. The put on sleeve is shifted for welding and placed in the oven for heat shrinking for one minute. After that, the sleeve cools down, lies down in the protective plate of the coupling, and a spare optical fiber is superimposed.
Advantages of fiber optic cable
The main advantage of optical fiber is the increased speed of information transfer, there is practically no signal attenuation (very low), as well as the security of data transmission.
- It is impossible to connect to the optical line without sanctions. Any connection to the network will damage the optical fibers.
- Electrical safety. It increases the popularity and scope of such cables. They are increasingly being used in industry for the danger of explosions in production.
- It has good protection against interference of natural origin, electrical equipment, etc.
If you are trying to figure out what fiber is, then you definitely hit the right place!
Many Internet users use fiber optic wire to connect to the Internet.
However, practically no one knows what an optical fiber is, what it is and how it transmits information?
optical fiber is the world's fastest way to transfer data over the Internet.
An optical cable has a special structure: it consists of small thin wires that are separated from each other by a special coating.
Each wire transmits light, and the light, in turn, transmits data over the network.
Let's take a closer look at how to connect the Internet and configure its work yourself.
First of all, make sure you have fiber optics connected to your home. Next, order the network connection service.
Also, the terminal is equipped with two additional jacks for connecting an analog home phone and a few more jacks are needed to connect television from Rostelecom.
After connecting all the components, you should check the Internet connections on your computer:
- Go to command prompt as administrator. To do this, right-click the manipulator on the Windows icon, select the required item;
In today's world, information is of great importance. Culture, communication, life and economy are built on it. At the same time, the speed of obtaining information should be as high as possible in order to fully satisfy the demands of modernity and maintain the pace of development of new technologies. This is why most ISPs are replacing their wired systems with fiber optic cable.
Purpose
This type of conductor is designed only for the transmission of a light pulse that carries certain information. That is why it is used for data transmission, and not as a power supply system. At the same time, it allows you to increase the speed several times compared to a metal conductor, and during its operation it does not have side effects in the form of loss of quality over long distances or heating of the conductor. The biggest advantage is that the transmitted signal is almost impossible to influence from the outside, which means that it is not affected by stray currents and does not need to be shielded.
Operating principle
The work of such a conductor at home can be observed in fiber-optic night lamps. A light pulse passes through special conductors, which can have not only a certain frequency, but also a color. At this time, at the other end, it is received by a device that converts the signal into the required form.
Laying fiber optic cable
Currently, there are a large number of different types of this conductor, which differs in the type of twist, the presence of an additional sheath and armor. In fact, it can be said that a fiber optic cable has the same parameters as a conventional conductor of a similar type and requires the same laying process. However, at the same time, they try to avoid a large number of bends and turns, and also do not work in areas subject to strong mechanical stress.
Fiber optic cable installation
Unlike metal conductors, which are interconnected by twisting, this type of cable requires special couplings or connectors. This is due precisely to the method of data transmission and the material that requires precise docking. Such connection difficulties can be called the only drawback that fiber optic cable has. At the same time, its price is constantly decreasing, while the cost of metal conductors is constantly increasing.
Application area
Nowadays, this type of cable is often used to connect to the Internet. It allows you to get the highest data transfer rate, even at a considerable distance from the repeater, and ensure a stable connection. Most modern providers around the world are replacing all their old lines with new routes based on fiber optic cable. Such companies can offer their users high-quality and high-speed network connection, and therefore they are very popular.
